A new and complicated layer of gene regulation mediated by small RNAs has begun to revolutionize our understanding of how the cell regulates gene expression on the posttranscriptional level. An abundant class of small regulatory RNAs, termed microRNAs (miRNAs), that are approximately 19-22 nucleotides in length have recently been identified to play major roles in gene regulatory networks involving multiple biological processes including stem cell differentiation, organ development, signaling, disease and cancer. System Biosciences proposes the construction of a lentiviral-based method for the expression of antisense microRNAs ("Anti-miRs") that will functionally inactivate endogenous microRNAs. This type of system will enable researchers to begin the process of unraveling the complex regulatory circuits governed by microRNAs - enabling a better understanding of the roles that the microRNA may be playing in cellular development, cell patterning, signaling, and human disease. During Phase I of this SBIR research project, System Biosciences will develop a small library of 100 Anti-miR lentiviral expression constructs and demonstrate the successful expression of the small antisense microRNAs as well as knockdown of targeted, endogenous microRNAs. PUBLIC HEALTH RELEVANCE: This research will benefit public health by providing researchers the means to stably and permanently knockdown a given microRNA. This will enable the investigation of all the roles that a given microRNA may be playing in cellular development, cell patterning, signaling, and human disease. [unreadable] [unreadable] [unreadable]